What is bin bash in linux

Shell Scripting – Define #!/bin/bash

A shell provides an interface to connect with the system. When we use an operating system, we indirectly interact with the shell. While using a terminal every time on any Linux distribution system, we interact with the shell. The main function of the shell is to interpret or analyze Unix commands. A shell takes commands from the user and translates them into the kernel’s understandable form. In other words, it acts as a medium between the user and the kernel of the operating system. The kernel is a computer program that is considered as the main part of a computer’s operating system.

This article focuses upon the significance of #!/bin/bash on the top of a script.

Significance of #!/bin/bash:

This is known as shebang in Unix. Shebang is a collection of characters or letters that consist of a number sign and exclamation mark, that is (#!) at the beginning of a script. As discussed in the introduction part, the main function of a shell is to interpret the UNIX commands given by the user. Unix consists of numerous shells out of that bash is one of them that is widely used. It is the default shell assigned by Linux-based operating systems.

A script comprises several UNIX commands. Now, in each of the scripts, users are required to explicitly specify the type of shell they want to use to run their scripts. Now to explicitly specify the type of shell used by the script, Shebang is used. So we can use shebang, that is, #!/bin/bash at the start or top of the script to instruct our system to use bash as a default shell.

Let us consider it with the help of an example. A script is nothing but several commands. In the below example, the first line of the script starts with a hash (#) and an exclamation mark (!). It basically instructs the operating system to use Bash as a default shell to run the script. In the second line, we are printing “Hello World!” to the console.

// Using shebang to specify the OS to // use bash shell // myScript.sh #!/bin/bash # Bash script echo "Hello World!"

Difference between #!/bin/bash and #!/bin/sh:

The shebang, #!/bin/bash when used in scripts is used to instruct the operating system to use bash as a command interpreter. Each of the systems has its own shells which the system will use to execute its own system scripts. This system shell can vary from OS to OS(most of the time it will be bash). Whereas, when the shebang, #!/bin/sh used in scripts instructs the internal system shell to start interpreting scripts.

Below are some of the shebangs used for different purposes in shell scripts:

• #!/bin/sh: It is used to execute the file using sh, which is a Bourne shell, or a compatible shell
• #!/bin/csh: It is used to execute the file using csh, the C shell, or a compatible shell.
• #!/usr/bin/perl -T: It is used to execute using Perl with the option for taint checks.
• #!/usr/bin/php: It is used to execute the file using the PHP command-line interpreter.
• #!/usr/bin/python -O: It is used to execute using Python with optimizations to code.
• #!/usr/bin/ruby: It is used to execute using Ruby.

Источник

What does #!/bin/bash mean

If you have ever written, downloaded, or opened a bash script, surely you have come across a somewhat strange first line that not everyone knows what it means and why it should be put there. I am referring to #!/bin/bash. Well, in this article you will be able to know all the details about what it is called, what it is for, and if it is always the same or if there are some changes.

What is an interpreted language?

Un interpreted programming language it is one that does not need to be compiled to run, but can be run directly from the source code using an interpreter, which is nothing more than a program that can translate the code into machine-understandable instructions. This brings some advantages:

• Multiplatform: as it is not binary, it can be run on various platforms without modification, which is a clear advantage if we want the code to work on any system.
• Portability: if the interpreter is platform-ready, then the interpreted script or language will work on that platform.

However, these interpreted languages ​​also have its disadvantages:

• One is performance, as they need the interpreter always running in the background for it to work.
• The own dependence of the interpreter.

As an example of interpreted languages Some can be mentioned, such as Java, C#, JavaScript, Visual Basic .NET and VBScript, Perl, Python, Lips, Ruby, PHP, ASP, etc.

What is a script?

Shell Scripting: Practical Examples

Un script is just code created with an interpreted programming language to perform a task. It is generally a simple program, with an event of commands or orders that are executed sequentially.

What is #!/bin/bash (shebang)?

Script content on Mousepad

Finally, the subject of this article is that famous #!/bin/bash, which is known in Unix parlance as Shebang. Although this is the most common, it is not always necessary to use it for the script to work. Other projects also have their own shebangs, such as #!/usr/bin/env python3, #!/bin/sh, etc.

The aim of shebang is simply giving the full path of the shell, so that it can be located wherever the script is run. Also, as you can see, not only the path is determined in it, but also the interpreter, in these cases Bash, Python 3, and other interpreters to work with.

The content of the article adheres to our principles of editorial ethics. To report an error click here.

Full path to article: From Linux » Programming Languages » What does #!/bin/bash mean

Источник

Linux /bin/bash Shell and Script Tutorial

Linux Bash shell is the most popular shell. /bin/bash is the path and executable of the Bash shell. /bin/bash is a binary that is used in different ways to run and execute commands and scripts.

Script File Interpreter #!/bin/bash

In Linux and opensource world script files are very important. There are different types of scripting languages used to write script files. As file extension is just a label for a script file interpreter line is used to specify the scripting language. #!/bin/bash specifies that current file is a bash script which will be interpreted with the bash or interpreter /bin/bash

# and ! makes this line special because # is used as comment line in bash. ! is called

Alternative Shells

Bash is very popular shell but there are a lot of alternatives to the Bash. Here is some of them.

• SH is a very basic shell that provides fundamental features of the Bash.
• KSH is Korn shell which is similar to the Bash.
• CSH is mainly designed from C programming language.

Difference Between #!/bin/sh and #!/bin/bash

As stated previously bash binary is stored in the /bin/bash path in general. /bin/sh provides the SH shell which is downgraded with less functional version of the BASH.

Bash Shell Commands

Detailed information can be listed with the man command like below. This provides detailed information about the BASH shell and related commands.

Источник